Here’s the gist: The film, which will actually begin after the events of the Original Series, follows an elderly Spock as he travels back in time in pursuit of a rogue Romulan named Nero. The time period Nero is traveling to takes place before the Original Series, when a young James T. Kirk and Spock are graduating from flight school and the Enterprise is a brand-new starship. Nero plans on assassinating Kirk before he goes on to screw over the Romulans, as seen in the many episodes of the Original Series.
Greg Dean Schmitz of rottentomatoes.com points out that the plotline leaves open the possibility of creating a completely different Star Trek universe if, say, something in the past is changed to the point where the Original Series never actually happens the way we saw it. I don’t think I like the idea of completely wiping away the events of the Original Series. But it might be kind of cool to revitalize the series by creating something of an alternate reality, as though the Original Series still exists within the Star Trek universe, but simply on another plane of existence. That idea would certainly be within the limits of Star Trek canon. In fact, if that’s the case, the new film wouldn’t even really be considered a “reboot.” Either way, with this film J.J. Abrams is either going resurrect Star Trek or bury it for good.